1. Field of the Invention
The present invention relates to fluid operated pressure oscillation generators of the type wherein a diaphragm is biased against a seat in a diaphragm housing by means of a cover detachably mounted to the housing and engaging the diaphragm at the periphery thereof. When a pressure fluid such as pressurized air is supplied to an inlet compartment in the diaphragm housing, surrounding the seat, the diaphragm operates as a valve in cooperation with the seat to control the fluid flow to an outlet passage inside the seat, which joins a resonator, such as a resonator horn.
2. Description of the Prior Art
Pressure oscillation generators of this kind are used for cleaning spaces in furnaces and process apparatus as well as other similar spaces through which gases are flown such as hot flue gases from combustion processes and exhaust and waste gases from chemical processes with dust and other fine particulate material entrained therein, which tends to deposit on the surfaces of the space passed by the gas and to form a coating on such surfaces. The coating forms an insulation layer on the heat exchange surfaces of the furnace or apparatus and therefore should be removed continuously or intermittently in order to maintain a high heat exchange efficiency. This type of cleaning is often called "sonic cleaning".
In sonic cleaning the coatings which may be hard and compact and may firmly adhere to the surfaces are actuated mechanically by the air propagated pressure oscillations transmitted from the pressure oscillation generator so as to be loosened from the surfaces and fall down to the bottom of the space to be cleaned. The oscillations involved may have a frequency in the audible frequency range or in the infrasonic frequency range (below about 20 cps).
When pressure oscillation generators of the type referred to are used for sonic cleaning in the manner described they are mounted in a wall of the space to be cleaned with the resonator opening into the space to transmit the pressure oscillations thereinto, while the diaphragm housing is located on the outside of the wall. Since the generator is subject to normal wear and also may be exposed to abnormal temperature conditions due to heat radiation from the space to be cleaned, it must be serviced from time to time for maintenance and repair including replacement of wearing parts usually the diaphragm which is the most easily damaged element of the generator. Then, it is of course necessary to remove the cover engaging the diaphragm, and when the cover as well as the diaphragm are removed from the housing, a connection will be established between the space to be cleaned and the surrounding atmosphere through the resonator and the passage inside the seat. If the space is at over-pressure as it usually is, hot and/or health-endangering gases may be expelled from the space as a back flow through the diaphragm housing in the form of a focused jet which may hit the person servicing the generator.